Cardiopulmonary resuscitation (CPR) is an emergency procedure to restore blood circulation and breathing in a person who is in cardiac arrest or ventricular fibrillation. According to the resuscitation guidelines, CPR involves clearing and opening the patient's airway, providing rescue breathing (where the rescuer provides airflow by exhaling into the subject's mouth or nose) or ventilation with a manually operated bag-valve or powered portable ventilator apparatus for the patient, and applying chest compression at a rate of about 100 per minute in an effort to create artificial circulation in the systemic and pulmonary vessels. The external chest compression creates in the thorax a positive pressure on the heart and consequently presses blood from the heart chambers into the blood vessels. During the release of the chest compression the thorax recoils and permits a refilling of the heart chambers with venous blood. CPR may succeed in inducing a heart rhythm. CPR is continued until the patient has a return of spontaneous circulation (ROPC). If the spontaneous circulation is not re-established the person will die within a few minutes.
Ventilation is a key component of CPR during treatment of cardiac arrest. Venous blood returns to the heart from the muscles and organs depleted of oxygen (O2) and full of carbon dioxide (CO2), Blood from various parts of the body is mixed in the heart (mixed venous blood) and pumped to the lungs. In the lungs the blood vessels branch up into a net of small vessels surrounding tiny lung sacs (alveoli). The net sum of vessels surrounding the alveoli provides a large surface area for the exchange of gases by diffusion along their concentration gradients.
It is very difficult to perform consistent high quality manual CPR. Since CPR quality is key for survival there is a strong drive to have an automated device to replace less reliable and long duration manual chest compressions; in this regard, automated CPR (A-CPR) systems were introduced in the market recently.
Automatic ventilators capable of delivering desired airway pressures for use during CPR are also known. For example, U.S. Pat. No. 4,326,507 describes a combined chest compressor and ventilator that delivers a ventilation over a number of compression cycles and then delivers another series of compression cycles during the period between ventilations.
Known ventilation devices (also referred to in this context as ventilator, or resuscitator) do not function well while chest compressions are being applied. The known device follows a pre-determined, fixed ventilation procedure, and the person, e.g., a paramedic, who is applying the chests compressions to the patient, has to synchronize with this procedure. Applying chest compressions is a task that wears out any person very fast and the synchronizing quickly becomes harder and harder. Compressions of the chest may lead to high pressure peaks in the patient's airways that usually give rise to alarms in the ventilation device. If the person continues to apply the chest compressions asynchronously with the ventilation cycles of the ventilation device, there is a high probability that the positive ITP pressure during chest compression counteracts the positive pressure provided by the ventilation system which consequently prohibits an airflow into the lung. The typical dead space of the airway of adults is about 150 ml. If the ventilator cannot provide a tidal airflow volume higher than the dead space the CO2 enriched air cannot be exchanged by oxygen-rich air.
While the current American Heart Association recommendation is two consecutive ventilations every thirty compressions, that recommendation was promulgated in large part because it was found that the delays due to switching back and forth between compressions and ventilation by rescuers was resulting in insufficient levels of chest compressions and the resultant circulation. It is desirable, in the case of mechanical devices to integrate the functions of chest compressions and ventilations.
EP 0 029 352 discusses various CPR procedures for employing ventilation, and advocates a specific one thereof. This publication discloses an apparatus for conducting the specific CPR protocol. The apparatus comprises a combination of a reciprocal cardiac compressor means for cyclically compressing a patient's chest and a ventilating means for inflating the patient's lungs to a relatively benign limiting pressure over a period of time encompassing at least one cycle of the compressor means. Both the cardiac compressor and the ventilator of the CPR apparatus are pneumatically operated and pneumatically controlled.
A-CPR devices haven't been able so far to ensure the delivery of a CPR procedure capable of substituting manual CPR; the main problems are the difficulties in properly fitting the device to the patient, especially in situations in which it is not possible to rest the patient in a stable, flat surface. Moreover, the patient interface of the A-CPR itself needs to be adjusted to the patient size, which may substantially delay the procedure. Furthermore, the use of an A-CPR device in combination with a mechanical ventilator is even more complicated due to the encumbrance generated by two different devices, especially when the rescuer has to reach the patient in hard to reach locations.
US 2012/118285 A1 relates to a ventilator configured to provide ventilation therapy for persons suffering from respiratory and breathing disorders, such as respiratory insufficiency and sleep apnea. U.S. Pat. No. 5,988,166 A discloses another ventilator apparatus for assisting or producing ventilation of the lungs of a patient.
U.S. Pat. No. 5,056,505 A relates to chest compression devices, such as a chest compression vest, which aid in the loosening and elimination of mucus from the lungs of a person, particularly people affected by cystic fibrosis.
U.S. Pat. No. 5,692,498 A discloses devices and methods used in conjunction with external chest compression and decompression as a part of CPR procedures. In particular, the devices and methods disclosed therein aim at increasing cardiopulmonary circulation induced by chest compression and decompression when performing CPR.
US 2014/180036 A1 describes a wireless sleep apnea treatment system for predicting and minimizing, or averting, sleep apnea episodes.